There is an urgent need to find alternative feed resources that can further substitute fishmeal in Atlantic salmon diets without compromising health and food quality, in particular during the finishing feeding period when the feed demand is highest and flesh quality effects are most significant. This study investigates efficacy of substituting a isoprotein (35 %) and isolipid (35 %) low fishmeal diet (FM, 15 %) with Antarctic krill meal (KM, 12 %) during 3 months with growing finishing 2·3 kg salmon (quadruplicate sea cages/diet). Final body weight (3·9 (se 0·04) kg) was similar in the dietary groups, but the KM group had more voluminous body shape, leaner hearts and improved fillet integrity, firmness and colour. Ectopic epithelial cells and focal Ca deposits in intestine were only detected in the FM group. Transcriptome profiling by microarray of livers showed dietary effects on several immune genes, and a panel of structural genes were up-regulated in the KM group, including cadherin and connexin. Up-regulation of genes encoding myosin heavy chain proteins was the main finding in skeletal muscle. Morphology examination by scanning electron microscopy and secondary structure by Fourier transform IR spectroscopy revealed more ordered and stable collagen architecture of the KM group. NEFA composition of skeletal muscle indicated altered metabolism of n-3, n-6 and SFA of the KM group. The results demonstrated that improved health and meat quality in Atlantic salmon fed krill meal were associated with up-regulation of immune genes, proteins defining muscle properties and genes involved in cell contacts and adhesion, altered fatty acid metabolism and fat deposition, and improved gut health and collagen structure.

The goals of ecosystem based management (EBM) are strategically ambiguous, meaning that they require interpretation to identify objectives for ecosystem state. Ecosystem states that are useful for achieving such objectives are known as reference points. Soft reference points specify both a state and a probability of the ecosystem being in that state. They are used with simulation models to identify management measures for which the risk of the ecosystem entering an undesirable state is below a specified level. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is responsible for the EBM of Antarctic krill fisheries. CCAMLR used soft reference points for the krill stock in the Scotia Sea and southern Drake Passage to set a regional catch limit. However, this catch limit needs spatial subdivision to protect predators from localized depletion. Model-based evaluations of different options for subdividing the catch limit used illustrative reference points to assess the depletion risk to multiple predators. This study demonstrates that the apparent risk is sensitive to the choice of reference point and method for aggregating modelled predators. EBM practitioners and stakeholders need to be aware that these factors could therefore bias comparisons of management measures. Nonetheless, qualitative distinctions between different spatial subdivision options are relatively consistent except at high levels of aggregation and extreme reference points. This study also demonstrates a lack of generality in the relationship between current and future ecosystem state. Thus, the EBM goal of maintaining ecosystem resilience implies different reference points for the current state of different ecosystem components. Despite early progress in defining soft reference points for the krill stock, CCAMLR has not yet defined reference points for krill predators. Structured dialogue aimed at identifying collective objectives might be necessary to achieve further progress in CCAMLR and other EBM organizations.

Pseudochaenichthys georgianus is a member of the unique Channichthyidae family of fishes, which lack haemoglobin. The distribution, length-frequency and summer diet are described from 14 bottom trawl surveys undertaken in the summers between 1986 and 2006. Pseudochaenichthys georgianus (50–590 mm TL) were caught throughout the South Georgia shelf from depths of 76–370 m, but very few specimens (< 1%) were caught on the Shag Rocks shelf. Multiple cohorts were present during each survey and length-frequency analysis of these cohorts suggests that growth is fast during the first 3–4 years. Stomach contents analysis (2005 & 2006) indicated that P. georgianus is a pelagic or semi pelagic predator, with the summer diet dominated by Antarctic krill (Euphausia superba). Fish (channichthyids and notothenids) were also taken, but were a relatively minor part of the diet.

Investigations in recent years of the ecological structure and processes of the Southern Ocean have almost exclusively taken a bottom-up, forcing-by-physical-processes approach relating various species' population trends to climate change. Just 20 years ago, however, researchers focused on a broader set of hypotheses, in part formed around a paradigm positing interspecific interactions as central to structuring the ecosystem (forcing by biotic processes, top-down), and particularly on a “krill surplus” caused by the removal from the system of more than a million baleen whales. Since then, this latter idea has disappeared from favour with little debate. Moreover, it recently has been shown that concurrent with whaling there was a massive depletion of finfish in the Southern Ocean, a finding also ignored in deference to climate-related explanations of ecosystem change. We present two examples from the literature, one involving gelatinous organisms and the other involving penguins, in which climate has been used to explain species' population trends but which could better be explained by including species interactions in the modelling. We conclude by questioning the almost complete shift in paradigms that has occurred and discuss whether it is leading Southern Ocean marine ecological science in an instructive direction.

Whilst interest in the economic exploitation of the Southern Ocean resources dates back to the last part of the 18th century scientific research into elements of the marine ecosystem only began in the mid 19th century. As far as plankton and benthos are concerned the great exploratory voyages and expeditions laid a firm taxonomic foundation on which later work was built. The most outstanding expedition contribution was from the Discovery Investigations. Concern about uncontrolled exploitation stimulated the SCAR BIOMASS programme which in turn led to CCAMLR with its modelling programmes and top predator monitoring. Recent research on pack ice communities has been aided by dedicated ice-capable research vessels whilst unmanned photographic techniques as well as SCUBA diving and experimental research facilities in the Antarctic have encouraged major research on benthos. International collaboration, interdisciplinary research and good ideas suggest Antarctic marine biology has a bright future.

Man's activities have impacted on the Southern Ocean ecosystem for more than 200 years. The exploitation of Southern Ocean resources has followed the same pattern as in other parts of the World Ocean with exploitation starting at the highest trophic levels when seals and whales were taken in the 19th and 20th centuries. After serious over-exploitation of these groups attention moved down the food web to begin exploitation of fish and krill from the late 1960s onwards. The establishment of international management regimes for whales (International Whaling Convention) in 1948 and the remaining marine resources (Convention for the Conservation of Antarctic Marine Living Resources) in 1982 were based on different perceptions of management, the former only considering management by species whilst the latter adopted management at an ecosystem level. These fundamentally different approaches, together with major political interference, have resulted in very different outcomes for management. The Scientific Committee of the IWC developed a sustainable management system, the Revised Management Procedure, in the first half of the 1990s which, however, is still awaiting inclusion into an overall management regime, the Revised Management Scheme, and its acceptance by the Commission. The IWC is now paralysed by political agendas that have nothing to do with scientific management. In contrast, after an early period of slow progress, CCAMLR has improved its performance substantially from the beginning of the 1990s onwards and is now hailed worldwide for its ecosystem approach to sustainable management.

The marine resources of the Antarctic region are of global significance. In managing Southern Ocean marine resources, especially fisheries, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has adopted principles that aim: to balance harvesting and conservation; to protect the needs of dependent species, and to avoid changes that are irreversible in 20–30 years. CCAMLR has pioneered ecosystem approaches to fishery and environmental management, through the incorporation of precaution and uncertainty into its management procedures and by establishing an ecosystem monitoring programme using indicator species and processes. This pioneering application of precautionary and ecosystem approaches in the management of harvesting has met with some success, notably in applying conservative yield models for toothfish and krill stocks and in establishing strict rules for undertaking new and exploratory fisheries. However, toothfish management has been recently compromised by Illegal, Unreported and Unregulated (IUU) fishing which is driven by forces outside the Southern Ocean. Southern Ocean harvestable resources are also subject to other global forces such as environmental changes, and their management systems remain very vulnerable to rapid shifts in worldwide fishery economics, and to inadequate management in adjacent areas, particularly high seas. CCAMLR needs quickly to develop the basis of more flexible and effective management to cater for rapid shifts in capacity and demand. The complementary task, however, is to raise the management standard of other Regional Fisheries Management Organisations (RFMOs) to those of CCAMLR if global high seas marine resources are to be sustainable for the rest of this century.

Commercial krill fishing has been undertaken in the Southern Ocean for twenty years. Recently the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) introduced a reporting scheme to summarize catch data from half degree of latitude by one degree of longitude rectangles. These data demonstrate that commercial fishing in the southwest Atlantic is concentrated in the shelf zone. Certain krill predators are also restricted to this area whilst collecting food for their young during the summer. Krill fishing takes place year round, moving northwards in winter as the ice edge advances.

The breeding season diet of the three surface-nesting petrel species on the Rauer Islands, Prydz Bay were examined. The stomach contents of cape petrel (Daption capense), Antarctic petrel (Thalassoica antarctica), and southern fulmar (Fulmarus glacialoides) were sampled by collecting regurgitates and by stomach flushing during the 1987/88 early chick-rearing period. Pleuragramma antarcticum and Euphausia superba dominated the diets of all species. By mass they constituted 78% and 22% of Antarctic petrel diet, 63% and 36% of southern fulmar diet, and 14% and 85% of cape petrel diet respectively. P. antarcticum increased in importance in the diet of Antarctic petrels during the course of the study, while E. superba became increasingly important in the diets of southern fulmars and cape petrels. Previous studies conducted during incubation consistently reported the diets as comprising chiefly cephalopods and euphausiids, whilst studies during chick-rearing have reported fish and euphausiids dominating, and very little cephalopod material.

The consumption of Antarctic krill (Euphausia superba) by an “average-sized” (male 6994 kg; female 8249 kg), sexually mature Minke whale (Balaenoptera acutorostrata) was estimated, from stomach capacity, ingestion rate and respiratory allometry methods. Estimates obtained from the stomach capacity and respiratory allometry methods differed by 17%–23%. An “average-sized” male Minke whale consumes 37.2 t of krill during a 90-day stay, and an “average-sized” female Minke whale consumes 56.2 t of krill during a 120-day stay, in Antarctic waters during the austral summer. It is estimated that the Minke whale population in the Antarctic (60°S and higher) consumes 35.5 × 106 t of krill annually.

In January 1985 a net sampling survey was carried out on the distribution and abundance of euphausiid larvae in the Prydz Bay region. Euphausia superba occurred in low abundance, probably due to sampling preceding the main spawning period. Thysanoessa macrura occurred throughout the study area in consistently high abundance. Euphausia crystallorophias was marginally more abundant within its restricted range. Distinct north-south variations in larval age and developmental stages of T. macrura were observed indicating regional differences in spawning. Euphausia frigida was mainly confined to the upper 200 m of the Antarctic Circumpolar Current. E. superba larvae produced north of the shelf break, between 70°–83°E, moved north-east into the Antarctic Circumpolar Current. Larvae originating on the shelf moved rapidly west in the East Wind drift. E. crystallorophias had the same westward dispersion, but some larvae appeared to return eastward via the Prydz Bay Gyre and remain in the region. The data indicate that most E. superba larvae, providing they survive injuries cold temperature an food deprivation, will leave the area, suggests that Prydz Bay krill may not be a self maintaining stock.

Icefish (Champsocephalus) were taken as bycatch during krill fishing operations from a research vessel. The data indicate that the bycatch of fish in the commercial krill fishery may be significant in some areas of the South Georgia shelf. The problem is thought to be least in open ocean krill fishing.

A female Antarctic krill loses 34% of its body mass when it lays a batch of eggs. This represents a considerable input of energy which was estimated using a combination of measured mass and energy differences in female krill and from the measured energetic content of ovarian tissue. Large (c. 50 mm) female krill lose 2.9–3.8 kJ each time a batch of eggs is laid. Calculations using this figure indicate that multiple spawning by Antarctic krill in a season would require above average phytoplankton concentrations (> 0.5 μg chl a 1−1) and filtration rates which are close to the maximum reported (> 10 l h−1).

Data from several summer research cruises in the Antarctic Peninsula region were analysed to calculate length (L50) and age at maturity for the Antarctic krill, Euphausia superba. Length at maturity L50 is defined as the length at which 50% of the krill stock attains sexual maturity. L50 values of 34.65–35.91 mm for female krill are the best estimates for the peak spawning season. Males attain sexual maturity later at L50 values of 43.35–43.71 mm. Length at maturity and length at first spawning are identical for krill. Comparisons with mean length-at-age data show that females mature in the third growth season (age class 2+), while males reach maturity in the fourth year (age class 3+). Both sexes show ‘knife-edge maturity’.

Laboratory studies have shown that Antarctic krill (Euphausia superba) shrink if maintained in conditions of low food availability. Recent studies have also demonstrated that E. superba individuals may be shrinking in the field during winter. If krill shrink during the winter, conclusions reached by length-frequency analysis may be unreliable because smaller animals may not necessarily be younger animals. In this study, the correlation between the body-length and the crystalline cone number of the compound eye was examined. Samples collected in the late summer show an apparent linear relationship between crystalline cone number and body-length. From a laboratory population, it appears that when krill shrink the crystalline cone number remains relatively unchanged. If crystalline cone number is little affected by shrinking, then the crystalline cone number may be a more reliable indicator of age than body-length alone. The ratio of crystalline cone number to body-length offers a method for detecting the effect of shrinking in natural populations of krill. On the basis of the crystalline cone number count, it appears from a field collection in early spring that E. superba do shrink during winter.

Diving behaviour of chinstrap penguins (Pygoscelis antarctica) was studied in four adults brooding chicks on Seal Island, South Shetland Islands, Antarctica. During foraging trips to sea, chinstrap penguins made shallow, short duration dives almost continuously, for the most part within 50 m of the surface. Diving effort was concentrated during the daylight hours (10h00-15h00), although a second peak in effort was seen around midnight (22h00-02h00). These peaks were possibly due to the constraints of visual location of prey, chick provisioning, or the need to take advantage of diurnal changes in krill swarm densities or behaviour. It was estimated that most effort was concentrated 3-20 km from shore. Dive depth and duration averaged 31.0 m (± 26.3m) and 72s(± 36s), respectively. Maximum dive depth and duration were 121m and 180s, respectively.

The diet of mainly adult and sub-adult male Antarctic fur seals (Arctocephalus gazella) was investigated during the austral winters of 1992 and 1993 using faecal (scat) analysis. Of samples containing identifiable prey remains (n = 376), c. 28% contained krill alone, c. 37% contained fish alone and c. 35% contained both krill and fish. The mean size of krill taken was smaller than in summer due to the absence of large adult krill of 55–60 mm total length. Of the 25 fish taxa taken, krill-feeding species predominated, especially in scats that also contained krill. Non-krill feeding species were more abundant in scats containing fish alone. The mackerel icefish (Champsocephalus gunnari Lönnberg 1905), which feeds mainly on krill, was the most important fish species in terms of absolute frequency (53%), frequency of occurrence (69%) and estimated biomass (47%); fur seals may have a significant impact on local stocks of this species. Cephalopods and pelagic fish (myctophids) were of minor importance in the diet (<2%). The importance of krill and krill-feeding fish species suggests that the male fur seals, which are present around South Georgia in winter, are targeting their foraging on a krill and fish community, probably associated with krill aggregations.

The stomach contents of demersal fish in late January 1982 were analysed. Samples were taken at 100, 300 and 500 m depth south of Elephant Island, Bransfield Strait and north of Livingston Island, and at 800 m to the east of Smith Island. Fifty four taxa of fish belonging to 11 families were collected. The diets of 2101 fish representing 38 taxa were examined. These were classified into three categories, fish feeders, krill feeders and benthos feeders. Fish prey species fed on krill and/or benthos. Krill was a major dietary component for 32 (84.2%) out of 38 taxa. Gobionotothen gibberifrons was distributed at all 10 stations (100–800 m in depth) and its diet comprised krill and benthos. The present findings verify the importance of krill in the Antarctic marine ecosystem and indicate that krill is consumed by benthic fish at greater depths than previously reported.

The Convention on the Conservation of Antarctic Marine Living Resources states as part of its objective the maintenance of ecological relationships and the prevention of irreversible changes to the ecosystem. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has implemented an Ecosystem Monitoring Programme (CEMP) for the Antarctic marine environment to give effect to this requirement. The design phase of the programme took three years. The programme has been fully implemented since 1987 and involves monitoring selected predator, prey and environmental indicators of ecosystem performance. The central aim of the programme is the detection of changes in these indicators and the interpretation as to whether these changes are due to natural events or the harvesting of marine living resources. The core of the programme is the acquisition, centralised storage and analysis of standardised monitoring data combined with a strong emphasis on empirical and modelling based research. This both modifies the monitoring approach in line with changing requirements and creates a sound scientific background against which to test the effects of management options on components of the Antarctic ecosystem. The development of procedures for translating monitoring results into management advice is a critical part of the programme. Management takes the form of the regulation of fishing activities. Since 1987 CEMP has collected data on six bird and seal species at 15 sites around the Antarctic. Up to 14 parameters of predator performance and 10 parameters of prey and environmental performance are collected at each site. The data sets collected by CEMP form an extremely powerful tool for understanding and managing the Antarctic marine ecosystem.

The diet of breeding white-chinned petrels was studied during the summers of 1996 and 1998 at South Georgia. Krill abundance/availability was high throughout 1996 but apparently low at the beginning of the 1998 breeding season. The diet of white-chinned petrels was similar between years and consistent with previous studies. Krill Euphausia superba (41–42% by weight) was the single most important prey item followed by fish (39–29%) and squid (19–25%). Meal mass was consistent (110 g in 1996, 119 g in 1998) between years but a significant decrease (46%) in feeding frequency in 1998 (0.54 meals day−1 compared to 0.75 meals day−1 in 1996) resulted in 19% less food delivered to chicks in 1998 than in 1996. Breeding success, however, was consistent between years at 44% and similar to that recorded previously at Bird Island. This is in contrast to black-browed and grey-headed albatrosses, both of which experienced almost total breeding failure in 1998. It is suggested that their varied and versatile feeding methods, together with their greater diving ability, capacity to feed at night and extensive foraging range, help white-chinned petrels minimise the effects of krill shortage.